Hecla Mining Co. has begun the process of permanently closing the Troy copper and silver mine in Montana’s Lincoln County. The mine was shuttered earlier this year.

Hecla is working with the U.S. Forest Service and Montana Department of Environmental Quality which are reviewing the reclamation plan for the Troy Mine. Hecla said it is confident that the physical work of closing the mine will begin next year. The reclamation plan was last updated in 2012 and spokesperson Luke Russell said little has changed in three years.

Seven people are currently working at the Troy Mine, including five who are ensuring that the mine, which operated from 1981 until this year, does not fill with ground water. The reclamation plan calls for the tailings area to be reseeded and that buildings, like the mine processor and offices, to be torn down. The mine portals will also be closed off and eventually the facility will fill with water. Russell said it could take two to three years to complete the shutdown. After that, the company will continue to monitor the water and environmental conditions for at least a decade, The Flathead Beacon reported.

While Hecla works on closing the Troy Mine, it’s also focusing on developing the Rock Creek Mine beneath the Cabinet Mountain Wilderness. Officials hope the mine will enable them to harvest copper and silver from one of the largest, untapped deposits in the world. Russell said the USFS is currently reviewing a supplemental draft Environmental Impact Statement and that a record of decision for the mine could be issued next year.

The Troy Mine closed in late 2012 after a series of underground rock falls. Revett struggled for more than two years to reopen the mine but eventually decided to close it. When Hecla purchased Revett earlier this year, the company announced it would permanently close the Troy Mine.